Project Summary The COVID-19 pandemic mitigation measures are difficult for those with substance use disorder (SUD), who are more likely to be unstably housed and do not have the economic means to comply. They may also not have access to correct communication messages about their risk. Agencies that provide services to those with SUD, such as syringe exchanges and other harm reduction organizations, have to weigh providing services to their clients against providing a safe workspace for their employees. These organizations have had to quickly implement response plans in tandem with a fast-moving pandemic, making potential mistakes in both messaging to clients and response to COVID-19. This has implications for how best to plan for a future outbreak. The primary objective of this study is to understand how best to provide harm reduction services to those with SUD in an infectious disease outbreak like COVID-19 by understanding how a large syringe exchange plans for and implements a plan and how clients conceptualize an outbreak, prioritize it within the context of their other daily risks, and determine what they expect from an agency that provides them harm reduction services. To do this, we will retrospectively investigate how COVID-19 was prioritized by clients of a Philadelphia syringe exchange and how organizational decisions about risk mitigation helped or hurt that prioritization. Utilizing the RE-AIM Implementation Framework as a guide, we will use a mixed methods approach with qualitative in-depth interviews, quantitative mathematically modeled maps from commercial marketing techniques, and a comprehensive review of planning documents, mitigation policies, and implementation plans. Specific aims are: 1. Assess perceptions of COVID-19 messaging. We will survey clients (n=100) and syringe exchange staff (n=50) and use perceptual mapping and vector modeling analysis to understand how communication of COVID-19 was processed and to inform development of more targeted and effective communication and messaging for future events.; and, 2. Analyze organizational response and COVID-19 plan implementation and develop an action plan. Using the RE-AIM Implementation Framework, we will perform an analysis of framework domains by conducting an implementation assessment. We will use survey data, conduct in-depth interviews with syringe exchange leadership (n=6), staff (n=15) and clients (n=15) and do a comprehensive review of planning documents and implementation of mitigation policies to understand how the planning and implementation was carried out. This analysis will then inform strategies for future responses through the development of an action plan. These methods aim to elucidate perceptions of COVID-19 messaging and assess decision making around the response from all stakeholders to better understand how to provide targeted communication and evidence-informed responses to potential new waves of this outbreak or similar future outbreaks.